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The Designer's Notebook: Preventing the Downward Spiral

"The rich get richer and the poor get poorer," my father used to say during the last stages of a family game of Monopoly. As he was the only one of us who really understood the strategy of the game when I was a kid, he tended to be the one who got richer.

Eight years ago I wrote a column called "Positive Feedback." In it I explained what positive feedback is in game mechanics: the tendency of a player's achievements to perpetuate themselves and strengthen the player. Positive feedback helps the rich to get richer in Monopoly. But what about the poor getting poorer?

Unfortunately, the terminology is rather confusing, because positive feedback that works against the player isn't called "negative feedback." Negative feedback is a mechanism that tends to keep things in the same place, preventing either growth or decay.

A household thermostat is a negative feedback device. If the temperature gets too hot, the thermostat turns on the air conditioning. If the temperature gets too cold, it turns on the heating. The thermostat tries to keep the air temperature at the same level all the time.

Marc LeBlanc illustrates the concepts of positive and negative feedback in game design very nicely with a combination of racing and combat -- think Mario Kart. If cars can shoot at each other with weapons that only fire backwards, the leader can shoot those behind him and they can do nothing to him.

This creates positive feedback for the leader and he tends to get farther ahead. If the weapons only fire forwards, the leader cannot shoot at anyone, while they're all shooting at him. This creates negative feedback: whoever is in the lead tends to be knocked out of it.

Negative feedback is a useful tool in game design; you can use it to put the brakes on positive feedback. (You don't want to make it too powerful, though, or you'll produce a stalemate.) But this column is about positive feedback in the downward direction: a mechanism that works to diminish, rather than increase, some value. In order to avoid confusion, I'm calling it the downward spiral.

In Monopolythe downward spiral begins when a player has to hand over properties to another player to pay a debt. The primary way that a player makes money is by charging rent when other players land on her property. When she has to give up a property, it deprives her of this source of income, which means that she is less competitive, and less able to deal with future bad luck.

Worse yet, the properties she once owned now belong to someone else, and have changed from being a safe place to stop (when they were hers) to being another place she has to spend money (if she lands on them in the future).

The downward spiral isn't completely bad, but it's depressing. (The Uruguayan persuasive game designer Gonzalo Frasca put this to good use in his brilliant Shockwave game, September 12.) Nobody likes the feeling that they have no chance of winning, and a slow grind down to failure isn't much fun.

I'm going to make some concrete suggestions about how to avoid creating downward spirals, and how to manage them if you must include one in your game.

The most obvious video game example of the downward spiral occurs when damaged units in a war game fight less efficiently -- firing shots less often or less accurately, for example. When a unit fights less efficiently, it doesn't destroy its enemies as quickly, so it tends to take still more damage, and so on.

In practice, we seldom implement this. Most war games follow Suggestion #1: their units fight at full efficiency right down to the last hit point. Arcade-style fighting games usually work the same way. Otherwise, the first player to make a mistake, or catch a bad break, will probably lose.

Of course, real life isn't like this: a person who has been injured fights far less efficiently than a fully healthy one. There have been a few heroic counter-examples -- men who went on fighting even while dreadfully wounded -- but they are exceptional, which is why those men get medals.

In modern practice, military units try to get wounded soldiers off the front lines as soon as possible. The first reason for this is humanitarian, naturally, but there's a second reason as well: wounded soldiers slow down the whole unit. It's better to have all the soldiers fighting fit, even with one less man, than to have a squad rendered inefficient by the presence of a wounded man. They, too, are trying to avoid the downward spiral.

If you don't allow damage to impair performance, then damage is simply a measure of how close a unit is to destruction. It doesn't feed back into the system. This suggestion applies whether performance is defined as fighting ability, productivity (such as that of a factory), or the performance of a vehicle.